Hertfordshire · England
Colney Heath Window Mastic
Window mastic across Colney Heath and nearby, with old sealant always removed completely and a one-year guarantee.
- Rain getting in at the frame or under the sill
- Whistling draughts around closed windows
- Black, perished sealant on frames
Different surfaces, different methods
uPVC windows
Fitters’ mastic on plastic frames is sometimes thin and rushed. It comes out, deep gaps get backing rod and the joint is resealed.
Timber windows & doors
On period timber windows, traditional sand mastic is sometimes the better choice. We can talk through the options.
Window mastic for homes and businesses in Colney Heath
There are two joints on most windows. Outside, the mastic keeps rain out; the internal joint closes the gap to the plaster and stops draughts. We seal one or both, depending on what’s needed. If you are dealing with untidy mastic left by window fitters and old mastic that has gone black or come away, we can put it right, whatever the surface.
Mastic can only go onto a dry, clean joint, so window work in Colney Heath is booked around the forecast. Let us know about access to all the frames, upstairs ones included.
The work is guaranteed for twelve months. If there’s a problem with our work within the year, let us know and we will sort it.
- Place
- Colney Heath (AL4)
- Region
- Hertfordshire
- Guarantee
- A year, on every job
- Price
- Quoted before any work starts
- Phone
- 0345 464 0079
- Updated
- 26 October 2026
Common problems we fix in Colney Heath
Timber windows bring their own problems. Mastic painted over many times cracks with the paint, and the wood moves with damp as well as heat.
Most people get in touch after spotting one of these:
- White mastic on grey or black frames
- Old mastic that has gone black or come away
- Gaps between the frame and the inside reveal
- Hard, cracked sealant around windows
In the older streets around Church of St Mark, the windows may be timber, sash or later replacements, and each needs the right sealant against the wall.
What to look for in a quote
- What guarantee comes with the work
- What product goes in the joint
- Who does the work, and how experienced they are
- Whether VAT is included
Work for landlords, hotels and businesses
We also work for businesses, from offices to washrooms and kitchens. On commercial sites, working times can be discussed when we quote.
We regularly work with letting and managing agents. Tell us the address, the job and how access works.
Window mastic in Colney Heath: local notes
With historic houses such as Hatfield House (about 2.3 miles north-east) nearby, there’s older building stock in the area around Colney Heath as well as newer homes. In older buildings, older frames set in brick or stone need a sealant that suits them, and sometimes that is traditional sand mastic. Colney Heath is part of Hatfield, one of the post-war new towns. Many homes date from the post-war decades, and many will have had their original windows replaced. That mastic ages as well, and sills and frame heads are where leaks start.
For site and facilities teams at buildings such as Colney Heath Junior Mixed Infant and Nursery School, larger buildings have plenty of frames, and the mastic around each one ages. For landlords with property near Welham Green station, cracked frame mastic tends to show up as a draught or damp complaint, so it’s worth checking between lets.
Colney Heath is about 2 miles south-west of Hatfield, in Hertfordshire. Wherever you are in the AL4 postcode area, we cover window mastic for homes and businesses. Colney Heath is one of 381 towns and villages in Hertfordshire we cover for window mastic. We also work in London, about 18 miles from Colney Heath.
Work in AL4 is quoted and booked the same way as anywhere else. Local streets include High Street, Fair View and Roestock Lane, and we cover them all. Neighbouring places we cover for window mastic include Sleapshyde (1 mile north-west), Welham Green (1 mile east), Smallford (1 mile north-west), Hatfield (2 miles north-east) and Tyttenhanger (2 miles west). We also work in nearby towns such as Watford (8 miles south-west), Hemel Hempstead (9 miles west), Stevenage (12 miles north), St Albans (3 miles west), Welwyn Garden City (5 miles north-east) and Harpenden (7 miles north-west).
Around Colney Heath
In Colney Heath, that means homes and buildings near Chalkdrawers Arms, Bishop's Hatfield Girls' School and North Mimms Park, among other places. The nearest railway station is Welham Green station, about 1.7 miles east of the centre. Other landmarks nearby include Hill End Hospital (2.3 miles west) and The Bunker at Hatfield Police Station (1.9 miles north). For a walk, there’s Verulamium Lake and Colney Heath Local Nature Reserve.
How to look after the new joints
No joint lasts for ever, but care makes a real difference. Our tips:
- Keep drainage slots and sill grooves clear
- Avoid blasting the frames with a pressure washer
- Walk round the house once a year and look at the joints
- Wash the frames with mild soapy water
Timber frames need their paint kept up, because bare, wet timber moves more and pulls at the joint. Paint up to the joint, not over the silicone.
Draughts get worse, not better. As the old mastic shrinks further, more air gets through, and a cold room gets colder. Resealing closes it.
Colney Heath: your questions answered
Will you come out to Colney Heath?
Yes, we do. We work across London and the South East, and smaller places are part of that. Longer journeys are simply planned in advance.
Can you help a landlord with a rental near Welham Green station?
Yes. We work for landlords and letting agents as well as householders. Just phone 0345 464 0079 or send us an email with the address and what needs doing, and we’ll give you a clear price.
Do you take out the old sealant first?
Yes. We cut out all the old sealant and clean the joint.
Can you do several jobs on one visit?
Of course. Combining jobs makes good use of the visit.
Where is Mr Mastic based?
Mr Mastic is based in Crawley. We cover Colney Heath and the rest of Hertfordshire, along with the rest of our area.
Can you match the sealant to my frames?
Yes, we choose a colour to suit the frame. Anthracite grey, black, brown and white cover most frames, with clear as an option.
Will you leave a mess?
Not at all. The area is protected while we work and cleaned up afterwards.
How long before the joint can be used?
That depends on the sealant used, so please follow the time we give you.
What affects the cost of window mastic
Some jobs are bigger than they look, and some smaller. What affects the quote:
- The type of sealant required
- Whether old sealant or filler has to be cut out
- The number and length of the joints
- Mould in or behind the old joints
Rather than a set price list, we price the job in front of us: the amount of work, the old material and the access. You will know the price before we begin.
What we need to know
Photos by email are helpful but not essential. Please mention:
- If someone has resealed it before
- What the problem is, such as mould, gaps, leaks or cracking
- Access, such as stairs, a lift or height
- The address or postcode of the job
To get a quote, phone 0345 464 0079 or drop us an email and tell us where the job is and what the problem looks like. You’ll have a clear quote before we start.
What sealant work can’t fix
A few problems are outside what sealant work can do:
- A door that needs adjusting, rehanging or new seals
- A sash or casement that won’t close properly
- A failed sealed unit that has misted up
If in doubt, phone 0345 464 0079 or email us and we will say what we think.
Joints and surfaces we work on
- uPVC windows
- Aluminium frames
- Composite doors
- Window sills
- Timber windows & doors
- Patio & French doors
Also near Colney Heath
Other services in Colney Heath
What we do, step by step
On the day, we look over the joints with you first, so you know exactly what we’re doing. Surfaces next to the work are protected before any work begins. Most jobs take a morning for a couple of windows and a door. Somewhere like Colney Heath needs a little journey planning: tell us about narrow lanes, gates, long drives and where we can park. Everything for the job comes with us, so a second trip is avoided where possible.
- We check how each frame can be reached safely.
- All the failed sealant is cut away, along with any loose debris.
- Frame and wall are cleaned and must be dry before sealing, and primed where the sealant calls for it.
- Deep voids are backed, then the sealant is gunned in.
- We tool the joint so water runs off, then clear up.
Getting ready for the visit
- Move anything stored near the joints
- Plan for the work area to be out of bounds to pets and children
- Tell us about access, such as stairs, a lift or high-level joints
How to get a quote
Every job is quoted individually, so start by telling us what you need. Just phone 0345 464 0079 or send us an email with the details, and pictures are welcome.